Glutathione (gamma-L-glutamyl-L-cysteinyl glycine) is a substance which is present widely in organisms. In addition to being used as a coenzyme, it is known to have a detoxifying action in the liver. Therefore, glutathione is widely used for drugs, health foods and cosmetics as a product, a raw material or an intermediate.
When glutathione is ingested orally, formulations such as tablet, granulations and liquid may be considered. And, liquid preparations are preferable because of ease of ingestion, and tablets are a preferred form because they are superior in portability, easy to dose in a constant amount and can be taken without worrying about taste.
In the manufacture of liquid containing glutathione, there is a need for a glutathione powder with high fluidity and a high solubility in aqueous solutions from the standpoint of handling in manufacturing processes and uniformity of constituents in the liquid preparation.
In the manufacture of tablets containing glutathione, there is a requirement for high fluidity in the glutathione powder used as the raw material from the standpoint of handling in manufacturing processes and uniformity of constituents in the tablet. Particularly when glutathione-rich tablets are manufactured, high compression moldabilities are required along with fluidity. When the fluidity is poor, there are cases where the tablets themselves cannot be manufactured. In addition, when powders with the large particle diameter are used simply to improve the fluidity, there is a possibility that troubles in tableting such as breaking, chipping and capping will arise. In addition, it is commonly known that it is difficult to obtain a tablet having a high level of tablet hardness.
In addition, as glutathione powders, crystalline powders are preferred instead of non-crystalline amorphous from the standpoint of hygroscopic properties, safety and the like. Furthermore, glutathione crystals with a small specific volume are desirable from the standpoint of easy transportation and costs.
Fermentation methods using microorganisms such as yeast and enzymatic methods (Applied Microbiology and Biotechnology, 66, 233 (2004)) are known as manufacturing methods for glutathione. Glutathione crystals acquired from a culture or reaction mixture that contains glutathione and is obtained by these methods are on the market, but there are difficulties in terms of fluidity, packing properties, tabletability, ease of dissolution and the like. There is a need for glutathione crystals with improvements to these points, but glutathione crystals with superior fluidity, packing properties, tabletability and ease of dissolution and a process for producing these crystals are not known.